Alzheimer's disease (AD) is one of the major health problems in the United States and as our population ages it will become more prominent unless measures to treat or prevent it are found. Understanding the pathogenesis of selective neuron degeneration in AD is the key to defining preventive or therapeutic measures. There is a rapidly increasing body of knowledge that indicates free radical-mediated oxidative damage is involved in the pathogenesis of AD. Our recent studies have demonstrated significant oxidative damage to brain lipids, proteins, DMA, and RNA in amnestic mild cognitive impairment, the earliest detectable phase of AD, indicating that oxidative damage is an early event in AD and not secondary to neurodegeneration. The major hypothesis of this proposal is that RNA oxidation in early AD is mediated in part by amyloid-beta peptide (AP) that promotes impairment of protein synthesis and neuron dysfunction. In Specific Aims 1 and 2, we will quantify RNA oxidation and aldehydic modifications in neurons in the progression of AD from normal to MCI to late AD (LAD), and in the APP/PS1 knock-in transgenic mice over time using immunohistochemistry, confocal microscopy, and antibodies against 8-OHG, acrolein/guanine adducts, and MC-1. In the same brain regions of normal controls, disease controls (frontotemporal dementia), MCI and LAD, and brain specimens from APP/PS-1 mice, we will quantify RNA oxidation in purified pools of rRNA, tRNA, and mRNA by GC-MS-SIM and acrolein-modified guanine in these pools using LC-MS-MS. In Specific Aim 3, we will determine the ability of toxic and non-toxic Ap from Core B to define RNA oxidation and acrolein/guanine adducts in cultured neurons and compare this with the RNA oxidation observed in vivo in Specific Aims 1 and 2. In Specific Aim 4, we will determine if the individual mRNAs oxidized in response to Ap in vitro are also oxidized in the brains of control subjects and MCI, LAD, and frontotemporal dementia patients. We will then determine whether the predicted proteins encoded by the oxidized mRNAs exhibit decreased expression and function in the progression from normal to MCI to LAD. Specific Aim 5 will define the ability of histone deacetylase inhibitors to ameliorate Ap-induced neurotoxicity in vitro and in the APP/PS1 transgenic mice. We have preliminary data in all specific aims indicating the feasibility of these studies. By conducting these studies in an unbiased manner and allowing the neurons and brain specimens to guide us, we will define how Ap promotes neuron dysfunction in AD. This study has the potential of identifying molecular targets for development of therapeutic agents aimed at reducing neuron injury and slowing the progression of or potentially preventing AD.